noise reduction

Hello, I found Adobes' Soundbooth was by far the best at initially removing noise. However, if you have a lot of unwanted noise you may need to use more than one program on one audio file for the best results. Although the programs are trying to do the same thing, you may still find that the more expensive program doesn't remove some noise very well that the less expensive program does. You can probably download a 30 day trial of Soundbooth to try.
Another program called Spectrum Lab is also very useful , and free, but a little bit technical. You can design your own filter to remove any frequency the crackling is on and by how much.